This works for the most part when there is a single child. Im assuming that the childHandler will actually create the substructure. You need to make minor modifications if you need multiple children. Also making this kind of API "very" extensible is non-trivial, because you have to reflectively determine what object to create based on the current object and the names of the children from the SAX events. If you have just one kind of xml document then this should suffice.
For more extensible APIs, take a look at: JiBX - http://jibx.sourceforge.net or XMLBeans - http://xmlbeans.apache.org/ for two APIs which do this sort of thing very nicely albeit very differently. On Thu, 16 Sep 2004, Jim Henderson wrote: > OK. It took bit to understand what you were saying but it works for me! > Thanks for the idea. > > Just to clarify: > > > public class DocumentParser extends DefaultHandler > { > ContentHandler childCH = null; > > startElement( > String uri, > String localName, > String qName, > Attributes attributes) > { > > if (childCH != null) { > childCH.startElement( uri, localName, qName, attributes); > return; > } > if (qName.equals("subStructure") { > childCH = subStructureContentHandler; > childCH.startElenent(uri, localName, qName, attributes); > return; > } > if ( ... > } > > characters( > char[] ch, > int start, > int length) > { > if (childCH != null) { > childCH.characters( ch, start, length); > return; > } > charArrayBuffer.write(ch, start, length); > } > > > endElement( > String uri, > String localName, > String qName) > { > if ( childCH != null) { > childCH.endElement( uri, localName,qName,); > > if (childCH.isDone()) { > childCH= null; > doSomething with the populated substructure; > return; > } > } > if ( ... > } > } > > -----Original Message----- > From: Nikhil Dinesh [mailto:[EMAIL PROTECTED] > Sent: Thursday, September 16, 2004 4:39 PM > To: [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: Re: parsing complex objects using Java SAX > > > > > I have data stream that contains complex objects (call this CO1). The > object > > contains sub-structures (call this SS1) that are used by other complex > > objects (CO2). Furthermore the sub-structures themselves may at times be > > standalone objects. > > > > I would like to write a content handler that can process the > sub-structures > > when they are standalone. I would like to reuse the sub-structures > content > > handler when processing to more complex object from its content handler. > > > > The examples I have seen chain the XMLReaders content handler for CO1 to > use > > the content handler for SS1 at the startElement() method. So far so good! > > But the ugly stuff occurs in the content handler for the sub-structure > SS1. > > The SS1 content handler endElement() method needs to know its parent > wrapper > > ends. At that point the XMLReader content handler is returned to the > parent > > object. > > > > This is not entirely true. The SAX events will always flow through the > parent ContentHandler. It is up to the parent to decide whether to pass it > on or not. For example when the first startElement is received, subsequent > startElements with no endElements should be passed on to or used to create > the child. When all these have received endElements(which are passed on) > and a further endElement is received the parent knows its content has > ended and that the parent's parent will not pass it any more events. Events > in > between can be passed on to the child. > > In other words the ContentHandlers themselves can be organized in a > treelike structure with events flowing down a path in the tree and being > absorbed by the node it is intended for. > > One way to accomplish this is by having your Objects implement > ContentHandler so reuse can happen. > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
